1. Field of the Invention
The present invention relates to a method of forming a formlocking connection of two telescopic tubes and a formlocking connection formed thereby.
2. Description of the Prior Art
Two telescopic tubes can be used, e.g., for forming a steering column of a motor vehicle. At that, the two tubes are so arranged relative to each other that in case of an accident, a frontal collision, they are pushed toward each other. Thereby, it is insured that in the case of a frontal collision, the steering column does not present a danger for the driver. The steering columns should be cheap in production, and for their manufacture, the use of simple, inexpensive semi-finished workpieces should become possible. The machinery processes should be reduced to a minimum in order to keep the manufacturing costs low. Despite of being formed of two parts, the steering columns should not have any rotational backlash. In addition, the steering column, as it has already been discussed above, should be able to reduce its length when a predetermined force is applied to the column as a result of a collision, with the length reduction being effected by displacement of the two tubular parts of the column toward each other.
There exist two type of motor vehicle steering columns. In one type, in case of a collision, the impact energy is transformed into work of deformation. In another type, in case of a collision, the impact energy is converted into friction and is thereby converted into heat energy. The two types of the motor vehicle steering columns are disclosed in numerous publications. Thus, e.g., the first type of a motor vehicle steering column, in which the impact energy is transformed into work of deformation, is disclosed in German publication No. 4,017,995, British Patent No. 1,156,426 and U.S. Pat. No. 3,504,567. However the structure of the steering column disclosed in the above-mentioned documents is very expensive, as is the process for its manufacture.
Accordingly, an object of the present invention is a method of manufacturing a steering column, in which the impact energy is transformed into work of deformation, which is inexpensive and can be effected with the use of simple tools.
Another object of the present invention is a form locking connection of tubular parts forming the steering column, which insures a backlash-free connection of the two tubular parts.